1. Field of Invention
The invention relates to an ink-jet printer, and more particularly, to an ink-jet printer that transfers large amount of print data speedily and stably.
2. Description of Related Art
A known ink-jet printer of an ink tube supply type is disclosed in Japanese Laid-Open Patent Publication No. 59-73953. Such an ink-jet printer includes a print head unit provided with an ink-jet print head. The ink-jet print head has an ink nozzle from which ink is ejected to perform printing onto a paper sheet. The print head unit is mounted onto a carriage. The carriage is driven by a motor to move the print head unit. Signals for driving the print head are transmitted from a control circuit, through signal input lines of flexible cables.
Referring to FIG. 7, signal flow paths to the print head will be described. FIG. 7 is a block diagram showing signal flow paths between an electric control circuit provided in a printer body and an electric receiver circuit provided in the print head unit. As shown in FIG. 7, a circuit board 20 is provided separately from the carriage in the printer body and includes a control circuit 21 that controls the print head. Another circuit board 22, provided on the carriage, includes a receiver circuit 23 that receives signals transmitted from the control circuit 21. The control circuit 21 and the receiver circuit 23 are connected by various signal lines. The signal lines connected to control circuit 21 and the receiver circuit 23 are, for example, a power supply wire V1 that carries the voltage (30 V) required to drive actuators of piezoelectric elements, and a power supply wire V2 that carries the voltage (5 V) required to drive a control circuit provided in the receiver circuit 23, as well as a flexible flat cable formed of an insulating sheet on which a plurality of image signal lines S1 to Sn are printed with an electrically conductive material.
In the above-described print head, when respective drive voltages are applied through the power supply wires V1, V2, and signals are provided to the image signal lines S1 to Sn, in the state that an ink passage is filled with ink, a voltage is applied to corresponding actuators. Accordingly, the actuators are deformed so as to instantaneously decrease the volumetric capacity of the ink passage. As a result, the ink in the ink passage is ejected from the ink nozzles in the form of a droplet.
In recent years, it has been required that a large amount of data be transmitted to the print head at high speed, to accommodate a multi-level gray scale printing, as well as high-speed, high-quality, high-resolution and multi-color printing, as is performed in the ink-jet printer using six colors of ink disclosed in, for example, U.S. Pat. No. 6,145,961. If the number of the ink nozzles needs to be increased or the number of the signal lines is increased to accommodate the multi-level gray-scale printing, the cable including the signal lines S1 to Sn becomes wide. Such a wide cable prevents the carriage from moving smoothly and can even make the physical size of the printer larger. When a large amount of data is transmitted at high speed through the electrically conductive signal lines, a signal waveform is affected by the electromagnetic interference, or radiant noise is generated to the outside. When the electric signals are transmitted at high frequencies equal to or greater than 100 MHz through the electrically conductive signal lines, a shield device is required as a remedy to the radiant noise.
When an ink-jet printer has a signal flow path to transmit data concerning the status of the print head unit, including the print head, such as the heat generated in the driver circuit board by driving the print head, the amount of ink remaining in an air trap unit, and the presence or absence of air in the air trap unit, from the receiver circuit 23 to the control circuit 21, an additional signal line is required to transmit the data. Such an increase in the number of the signal lines leads to the printer becoming large in size.
In the light of the foregoing, it is desirable to provide a compact ink-jet printer that controls a print head unit thereof according to the conditions of the print head unit, and to enable a large amount of data to be transmitted speedy and stably.
According to one aspect of the invention, an ink-jet printer may include a printer body; a print head unit that includes a print head for performing printing onto a recording medium and a carriage on which the print head is mounted; a control circuit that is provided in the printer body separately from the print head and controls the print head unit; a receiver circuit that is provided on the carriage and receives a signal from the control circuit; a first transmission member that converts drive data for the print head into a light signal, transmits the light signal, and is provided in the control circuit; a first reception member that receives the light signal transmitted from the first transmission member and converts the light signal into an electric signal and is provided in the receiver circuit; a second transmission member that converts status data for the print head unit into a light signal and transmits the light signal and is provided in the receiver circuit; a second reception member that receives the light signal transmitted from the second transmission member and converts the light signal into an electric signal and is provided in the control circuit; and an optical fiber through which the light signal from the first transmission member and the second transmission member is transmitted to the first reception member and the second reception member, respectively.